UDP proxy for upstream health monitoring

```yaml
admin:
access_log_path: /tmp/admin_access.log
address:
socket_address:
protocol: TCP
address: 127.0.0.1
port_value: 9901
static_resources:
listeners:
- name: listener_0
address:
socket_address:
protocol: UDP
address: 0.0.0.0
port_value: 1234
udp_listener_config:
downstream_socket_config:
max_rx_datagram_size: 9000
listener_filters:
- name: envoy.filters.udp_listener.udp_proxy
typed_config:
'@type': type.googleapis.com/envoy.extensions.filters.udp.udp_proxy.v3.UdpProxyConfig
stat_prefix: service
matcher:
on_no_match:
action:
name: route
typed_config:
'@type': type.googleapis.com/envoy.extensions.filters.udp.udp_proxy.v3.Route
cluster: service_udp
upstream_socket_config:
max_rx_datagram_size: 9000
clusters:
- name: service_udp
type: STATIC
lb_policy: ROUND_ROBIN
connect_timeout: 0.25s
load_assignment:
cluster_name: service_udp
endpoints:
- lb_endpoints:
- endpoint:
health_check_config:
port_value: 64879
address:
socket_address:
address: 1.1.1.1
port_value: 64879
address:
socket_address:
address: 1.1.1.1
port_value: 64879
- endpoint:
health_check_config:
port_value: 64879
address:
socket_address:
address: 2.2.2.2
port_value: 64879
address:
socket_address:
address: 2.2.2.2
port_value: 64879
```
64879 is a service port for Wireguard, which was started on 1.1.1.1 and 2.2.2.2 respectively. Now, stop the Wireguard service in 1.1.1.1 and use curl http://127.0.0.1:9901/cluster I see that the health status of this IP is still normal. May I ask how to solve this? How to perform health check on UDP 64879 port?